To enhance the social experience among participants, the organizers of the Wikimedia Hackathon 2017 Vienna have created a Telegram Group Chat "Wikimedia Hackathon" @wmhack, which everyone can join via t.me/wmhack.
This group can be re-used for other events.

When you announce communication tools/channels/groups/social media (e.g. Telegram, etc.), you should also publicize that all hackathon communication tools are covered by the Friendly Space Policy and Code of Conduct.

Advantages of Telegram: While you need to have a phone number to use Telegram, you do not need to share your number with people (as opposed to e.g. WhatsApp).

What to post on Telegram:
Organizers share news and updates via the group, participants can use it for ideas, suggestions, chatter, and to organize themselves.

Set it up in 2 minutes: (If you have Telegram already, you can skip step 1)